Objective To evaluate the clinical efficacy of total hip arthroplasty (THA) with no femoral shortening oste?otomy for unilateral CroweⅣ developmental dysplasia of hip. Methods From October 2007 to January 2010, 32 patients with CroweⅣdevelopmental dysplasia of hip in one side underwent THA, including 20 females and 12 males, with an average age of 49.4 ± 9.7 years (range, 23-60 years). There were 15 cases as normal and 17 as mild developmental dysplasia of hip in the other side. The THA were performed with requisite soft tissue release and direct leverage using an elevator but with no femoral shorten?ing osteotomy. The patients' satisfaction, Harris hip score, bilateral leg?length discrepancy and pelvic obliquity was used to assess the clinical results. Results All of patient were followed up for 1-6 years, average 4.0 ± 1.5 years. No loosening or failure of component occurred by the end of follow?up. The Harris hip score was improved from preoperative 36.5±10.3 (20-63) to 89.8± 4.9 (80-97), and the excellent and good rate was 100% (excellent 16 cases, good 16 cases). The satisfactory rate was 93.8%(30/32). The leg?length discrepancy of the bilateral sides and the pelvic obliquity was corrected gradually and the gait returns to normal. Nine cases have valgus knee after THA and 4 cases of them felt uncomfortable after long?distance walk. Femoral nerve injury occurred in 2 cases. All of cases recovered after 1 and 3 months respectively. No infection and dislocation oc?curred. Conclusion THA with no femoral shortening osteotomy can achieve good clinical results in patients with unilateral CroweⅣdevelopmental dysplasia of hip. The discrepancy of leg?length will be diminished with the correction for pelvic obliquity.

Objective To assess the functional restoration in patients with developmental dysplasia of the hip (DDH) who underwent hip resurfacing arthroplasty and to determine whether greater abduction angle of the acetabular component is relat?ed to larger diameter of femoral head component. Methods We reviewed 34 DDH cases (9 hips of 8 males and 25 hips of 24 fe?males, mean age 44.6±11.85 years at the time of surgery) on whom we performed hip resurfacing arthroplasty (HRA) from October 2006 to September 2009. The total hip Arthroplasty (THA) group was consisted of 35 DDH cases (8 hips of 8 males and 27 hips of 25 females, mean age 43.7±10.4 years at the time of surgery). All operations were performed by the same doctor over the same peri?od. Assessment of the functional hip scores was conducted by Harris Hip Scores. A radiographic study was also performed to evalu?ate the implants stability and abduction angle of the acetabular components. All the data was analyzed with Kolmogorov?Smirnov method. Results The mean follow?up was 6.2 years in the HRA group. The Harris Hip Score improved from 54.9±13.2 to 97.3± 6.2 after the surgery. The mean abduction angle of the acetabular component was 51.6° ± 5.33°, hip flexion was 127° ± 6.9° and mean diameter of femoral head was 46.5±1.5 mm. The mean follow?up was 5.9 years in the THA group. The Harris Hip Score im?proved from 51.6±19.7 to 95.6±7.9 after the surgery. The mean abduction angle of the acetabular component was 43.9°±4.90°, hip flexion was 117°±4.2°. There was no failure of the prosthesis, peri?prosthetic fracture and infection in either group. There was sig?nificant difference in the abduction angle of the acetabular component (P<0.05) and flexion of the hip between the two groups (P<0.05). Conclusion Patients in the HRA group had a better functional restoration and larger range of motion. Furthermore, a larger diameter of femoral head component could be achieved by placing the acetabular component in a greater abduction angle, which may contribute to a better long?term stability.

OBJECTIVE: To understand the relationship between porosity, collagen fiber orientation and strength of the plated bone after rigid plate fixation and removal. METHODS: Seventy-two New Zealand white rabbits were used in this experiment. Eight animals served as control and the other sixty-four were plated on their intact left tibiae with stainless steel (316L) 4-hole plates to induce early osteoporosis. The plates were removed 2 months after internal fixation in 40 plated animals, 8 of which were sacrificed immediately following plate removal and the other 32 were killed in successive groups with 8 in each group 1, 2, 3 and 4 months after plate removal. The remaining 24 plated animals were killed at 3, 4 and 6 months after plate fixation. After sacrifice, the samples of plated bone were prepared for light microscope, quantitative histological analysis, polarized light microscope and biomechanical test. RESULTS: The internal fixation with a rigid plate could induce the regional osteoporosis which manifested both bone loss and disorganized bone structure (loss of the orientation of the collagen fibers) leading to decreased strength of the plated bone. Although the regional osteoporosis could recover gradually after plate removal, the bone structure remained disorderly even when the bone mass returned to normal. Delayed restoration of bone structure was related to delayed restoration of bone strength. CONCLUSIONS: Besides the bone loss, the disorganized bone structure is the main cause of decrease of bone strength after rigid plate fixation and removal.